Is it even worth it to buy less than 500W PSU's?

I am scouring craigslist looking for some scraps to finish my HTPC I am building. I will be using a mid tower case, and I found a Coolermaster 832 brand new for 50 bucks. I can also pick up a PC Power and Cooling Silencer 470 watt PSU for 25 dollars.

I know that this PSU will be enough for the HTPC, it will have a undervolted E5200, 8 GB RAM, a few 2TB harddrives, and a fairly modest GPU.

However, I just put together a system for myself with an i5-2500k, Asus P67 WS revolution, 8GB ram and a 256 GB crucial SSD. I will be keeping 1 7200 RPM harddrive along with my m4, and other then that, there are no other power requirements. No other harddrives, I have no optical drives, and probably 5-8 USB devices, 4 of which get external power.

The guy has 2 of these PSU's, and I can get both of them for $45.00. I know that 470 isn't a lot, but apparently these PSU's put out very consistent power, and they actually put out the wattage they are rated for (this one says 520 peak)

The only reason I am considering this PSU is because I am currently running my new RIG on a generic orion 485 watt PSU. Everything is stable, but I figure if I can get a quality PSU for cheap, I may as well do it.

The only thing that concerns me at this point is the videocard. I may end up putting my GTX 460 in the HTPC, and I am considering either a ATI 5850, or an ATI 5870 that I can get for a really good deal. I also have a possible line on a gtx 470, and am considering that as well. I went to this website: http://www.thermaltake.outervision.com/ and it looks like with all of my devices, and a GTX 470 I am at about 450 watts give or take. This is with my usage pegged at 100%, which my computer is 15-20 hours a day every day. I run folding@home on all 4 cores, as well as the GPU.

So what do you guys think? Is it just a complete waste of money to pick up these PSU's? I figure if anything it never hurts to have a spare around. I need my HTPC to be completely silent, and am running no fan on my CPU heatsink. If these PSU's are as quiet as they claim to be, and as quiet as the reviews on newegg say they are, then I feel like this is a good buy. Let me know if i am mistaken.

The Silencer 470 is an old design that's only 74% efficient, and is far more capacity than you need- your HTPC would probably run fine off as little as 150W. PCP&C Silencers are also not particularly quiet by modern standards.

I would probably consider a Corsair CX430 V2 or Antec Earthwatts Green 380 for the same $25, although neither one of those is dead silent either-- they are likely to be less noisy than the PCP&C Silencer 470.

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only thing that concerns me at this point is the videocard. I may end up putting my GTX 460 in the HTPC, and I am considering either a ATI 5850, or an ATI 5870 that I can get for a really good dea

Well, if you DO plan to put a high-powered video card in your box, that does change the power needs quite a bit.

HTPC will draw somewhere around 100W to 150W at the very most, maxed out. That's with a fast CPU and a few HDs and a decend video card (not top end / room heater from AMD or NVidia....) Get a 150W PSU or to be safe a 200W PSU, but a QUALITY PSU with a high efficiency rating.

I ended up purchasing a PC&P silencer 500 mk III. It was only $35.00 shipped, so I will be using this as my main power supply to power my i5-2500k/ATI 6870 rig. My HTPC will get my Orion 485 watt PSU as that should be more than enough.

A part of me kept thinking that if I am going to spend money on an item, I might as well make sure I can take it with me for my next build. I believe this PSU will last me for quite a while.

So for $85.00 total I was able to get a 500 watt modular PSU and the Coolermaster 832 stacker. Not too shabby!

This really makes me wonder why all of these power supply manufacturers routinely sell power supplies that are way more powerful than 550W if the only machines that'll ever draw that much are going to cost $2000.

So why is it? Do power supplies with more wattage sell better? Why shouldn't all of us average joes with mediocre $1200 computers with i5-3570Ks and GeForce 660 Tis get PSUs with only 400W of power?

This really makes me wonder why all of these power supply manufacturers routinely sell power supplies that are way more powerful than 550W if the only machines that'll ever draw that much are going to cost $2000.

So why is it? Do power supplies with more wattage sell better? Why shouldn't all of us average joes with mediocre $1200 computers with i5-3570Ks and GeForce 660 Tis get PSUs with only 400W of power?

The difference in manufacturing cost between a 400W and an 850W (or whatever) power supply of equal quality is tiny.

Given you can charge quite a bit more, and the natural appeal of a bigger number, it makes all the sense in the world from the manufacturers' perspective.

This. Video card makers tend to massively overinflate their PSU requirements because they can't predict if people buying their cards will use a quality power supply or a piece of utterjunk that can't even provide half its rated power.